This invention relates to a motor driven camera and to a motor drive unit removably attachable to the camera so as to form a system wherein the drive unit electrically winds the film in the camera, initiates release of the camera shutter, and the like.
In a motor driven camera, when the motor drive unit is removably attached to the camera body, it is necessary to transmit various control signals from the camera to the unit and from the unit to the camera. For this purpose, many electrical contact terminals are provided on both the camera body housing and the motor drive unit housing. In recently developed cameras, the use of many electronic devices in both the camera and the motor drive unit requires utilization of many signals transmitted therebetween. Thus, the number of interconnect terminals between the camera body and the motor drive unit tends to increase.
In general, a motor drive unit is attached to the bottom panel of a camera body housing by a fastener such as a tripod screw. Therefore, the aforementioned electrical contacts or terminals are arranged on the bottom panel of the camera housing and on the top panel of the motor drive unit casing with little protection from foreign particles such as dust and sand. Because these terminals are spring-biased, accumulation of a layer of particles on the interfaces betwen the contacts of the camera body and the drive unit is liable to cause insufficient electrical contact therebetween. Therefore, the larger the number of such signal transmission terminals, the lower the reliability of the resulting camera. Besides, as the bulk and size of a camera is reduced, it becomes more difficult to fit large numbers of terminals on the housing.
Even in a conventional motor driven camera, the various signals use a common return path to circuit ground. This has the effect of diminishing the number of interconnecting terminals. Further attempts at reducing the number of terminals involve, for example, generating a winding completion signal within the motor drive unit itself to obviate the necessity of transmitting this signal from the camera body to the unit in controlling the operation of the unit. However, the self-contained character of the completion signal within the motor drive unit increases the possibility of phase errors in synchronizing the operation of the camera body with the unit. In the past, this resulted in faulty operation of conventional motor driven cameras.